A molecular dynamics simulation study of crystallographic orientation and interfacial properties during nucleation of the austenite - Ferrite phase transformation

The study of the solid-state nucleation through experiment is often limited by small length and time scales and even today most of the solid-state nucleation mechanisms are estimated based on classical nucleation theory. In this study, we use the molecular dynamics (MD) method to study the nucleation of the BCC ferrite phase in pure Fe starting from a polycrystalline system of the FCC austenite phase. The simulation focuses on the heterogeneous nucleation occurring at grain boundaries. The grain boundary energy, the FCC-BCC interface energy and the crystallographic orientation relationship between the new and parent phases are monitored during the MD simulations. Consistent with previous experiments on steel, several special orientation relationships are found to dominate during the nucleation stage. The crystallographic orientation significantly affects the interface properties during the transformation process. In addition, a barrier-free heterogeneous grain nucleation phenomenon is captured and analyzed in this study.